Serbian Ombudsman Sasa Jankovic said in a report on Monday that Belgrade police refused on purpose to respond to calls from people who saw around 30 masked men armed with baseball bats and equipped with diggers tearing down buildings on the riverbank on the night between April 24 and 25 and allegedly beating up local residents.

After examining police documents and listening to recordings of police telephone conversations during the incident, Jankovic concluded that the police were complicit in the nocturnal demolitions.

“These omissions in the work of the police are not the result of individual mistakes, but were organised and implemented within the framework of a previously prepared plan,” Jakovic said in his report.

“Police officers and their superiors did not know or did not dare to reveal the identity of the party who ordered [the demolitions] to the Ombudsman,” he added.

The police telephone operator told concerned callers on the night of the incident that there were orders “from the top” that they should instead call the community police, who do not deal with serious criminal matters.

Jankovic said in his report that he also listened to a recording of a police officer asking his superior for help because of the amount of complaints from the public.

According to Jankovic, the policeman said: “This person who is being tied up has called the community [police] and they rejected him. Should we give him anything? Nothing? OK, nothing.”

The callers reported that on the night of the incident, around 30 masked men armed with sticks, stopped and searched them, tied them up and detained them in the Herzegovacka street area of Belgrade’s Savamala district.

The masked men also demolished a series of empty buildings – the Sava Ekspres restaurant, a family house, the Iskra company office and several others.

Rumours have suggested that the buildings were demolished in order to make way for the government-backed Belgrade Waterfront project, a major redevelopment scheme that will cover much of the south bank of the Sava river in the Savamala district.

Serbia’s Public Information Commissioner, Rodoljub Sabic, has called on the city authorities to explain what happened, but both the Belgrade police and Mayor Sinisa Mali have denied knowing anything about it.

“What happened there, if anything happened, will be established by the competent authorities,” Mali said on May 6.

Sabic said he has been threatened for asking for the case to be investigated.

“Continue to be interested in the actions of the people under the masks and you’ll have the opportunity to meet them,” said one alleged threat which Sabic posted on Twitter.

The president of the Belgrade’s municipal assembly, Nikola Nikodijevic, has questioned whether the incident even happened.

“Nobody reported anything to the police and what is certain is that nobody saw it, it just boils down to a story of few people,” Nikodijevic said on May 1.

While Serbia’s government sees the Belgrade Waterfront project as a major contribution to the city’s economic future, critics claim that its deal with Eagle Hills, a company based in the United Arab Emirates, was unconstitutional because it involved the suspension of Serbian laws in the area in which the project is to be built.

After the Ombudsman’s findings, the Let’s Not Drown Belgrade campaign group, the most persistent opponent of the Belgrade Waterfront project, scheduled a protest for Wednesday in front the city assembly.

Sources in the state prosecution told BIRN that a preliminary investigation is ongoing and when the police submit their report, the prosecution will decide whether it will initiate a full investigation.